Causes and preventive measures of electric shock o

Reasons and preventive measures for electric shock of welders during electric welding operation

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2) the no-load voltage of the welding machine mostly exceeds the safety voltage. For example, the no-load voltage of the commonly used AC arc welding machine is generally 70V. When the welder is sweating (especially in summer), his shoes and socks are wet, and the sole of his shoes is thin, the resistance of the human body drops to only about 1600. Once the welder's hand contacts the jaw, the current through the human body can reach 40 ~ 50mA, which makes the welder's hand spasm, and even can't get rid of it and get an electric shock. When the welder changes the welding rod, his hand contacts the welding tongs, while other parts of his body directly contact the metal structure and connect with the other pole of the electric welding machine, which is more likely to cause electric shock accidents

measures to prevent electric shock:

1) the shells of all AC and DC arc welding equipment must be grounded. In three-phase three wire system or single-phase system, protective grounding wire shall be installed; In the neutral point grounding system with three-phase four wire system, protective neutral line shall be installed

its requirements are also getting higher and higher. 2) the end of the secondary winding of the arc welding transformer connected with the weldment must also be connected or connected to zero. When the insulation of the primary winding and the secondary winding breaks down and the high voltage appears in the neutral connection, the weldment should never be grounded or connected to zero again. Otherwise, once the secondary circuit is poorly connected, the welding current in may fuse the grounding wire or neutral line, which will not only threaten personal safety, but also easily cause fire

3) welders must wear protective work clothes, insulating shoes and protective gloves as required during operation. Always wear leather gloves when replacing welding rods. It is forbidden to touch the conductor of the secondary circuit with hands and body. When the body is sweating and the clothes are wet, do not lean against the charged steel plate or sit on the weldment to work

4) when welding inside the metal container, the foot should be lined with a rubber insulating pad, and the working voltage of the lighting lamp should be lower than 12V

5) the following operations should be carried out after cutting off the power supply: changing the welding machine connector, changing the secondary return line, swinging the welding machine, replacing the fuse, and repairing the welding machine

6) the manual arc welding machine shall be equipped with an automatic power-off device for the welding machine, and its technical requirements are: the starting time of arc striking is 40ms; No load Voltage 18V; The power-off delay is within 10.5s; The starting sensitivity is 300 and 500 according to the needs of the project

7) the welding machine should work under the load duration allowed by the nameplate, and should not be overloaded for a long time